Atrial septal defect

Atrial septal defect (ASD) is a congenitalheart disease of dogs characterized by shunting of blood from the left to right atrial chambers of the heart. This can also occur due to a patent foramen ovale, which has the same clinical presentation.

ASD is a genetically heterogeneous disease and the genetic determinants remain to be identified[2].

This condition in dogs is relatively rare and is sometimes observed as part of the Tetralogy of Fallot. ASD does not produce severe hemodynamic lesions compared with ventricular septal defect[3].

Although most ASDs are a defect with communication between left and right atria, abnormal ASDs can occur as left ventricular-right atrial communications, known collectively as Gerbode defects[4].

Clinical signs are normally seen in young dogs (1 - 2 years of age) but can present at an older age with symptoms of generalized weakness, exercise intolerance, syncope and pale mucus membranes. A cough may be present intermittently.

A tentative diagnosis can be established by auscultation of a holosystolic heart murmur and radiographic evidence of cardiomegaly but definitive diagnosis requires use of M-mode and Doppler echocardiography.

Echocardiographs usually elucidate the septal defect and often shows concurrent right ventricular hypertrophy.

Treatment is usually conservative, with management of the secondary congestive heart failure, but surgical correction can be performed at specialty referral centers via cardiopulmonary bypass using biodegradable atrial septal defect occluders[10].